Repeated fuel filter clog, failing fuel pump, or ?

[csp]

Cut the filter open and see if it's clogged. The color of the fuel dripping out of it doesn't mean a thing.

I wouldn't suspect an injector issue at all. It would run very rough, not just quit.

If this problem re-surfaces, immediately crack the gas cap and see if the problem goes away. You may have a fuel tank venting problem, leading to a vacuum in the tank and lines to the point where the fuel pump will no longer have the power to pull fuel from the tank. Remember, as fuel is burned the volume it took in the tank has to be replaced by air. A problem with the venting system can prevent this from happening.

 

[St Runner]

When you change the filter it cures your problem, that tells me your problem is from the fuel filter back. Could be venting as csp says, could be debris although I don't think that is totally the problem. I think it is poor fuel pump pressure in combination with some blockage. Drop the tank. Change the pump. check all the fittings and hoses. As you said yourself it feels like an allover thing and not an individual cylinder and changing the filter fixed it. Drop the tank and figure out why you are not getting proper fuel delivery

 

[hour]

Cut the filter open and see if it's clogged. The color of the fuel dripping out of it doesn't mean a thing.

I wouldn't suspect an injector issue at all. It would run very rough, not just quit.

If this problem re-surfaces, immediately crack the gas cap and see if the problem goes away. You may have a fuel tank venting problem, leading to a vacuum in the tank and lines to the point where the fuel pump will no longer have the power to pull fuel from the tank. Remember, as fuel is burned the volume it took in the tank has to be replaced by air. A problem with the venting system can prevent this from happening.

CSP - I'll cut it open tomorrow, have to pick up some hack saw blades.

The problem did resurface the next morning.. so the 'fix' of once again swapping the fuel filter only lasted me for the duration of a 20 minute test drive. Took it for a 3 mile spin cursing, pulled in to a parking lot, and very quickly yanked the EFI relay, cranked, opened gas cap, and then buttoned back up. Idle was smooth and power back for about a mile.

Interesting theory on the venting - I already know I have the '99 messed up tank vent. I never have any problems with the gas pump shutting off until the usual 13-14 gallons, but I can hear the tank getting full ~10 seconds before the pump cuts off, and I can hear the fuel in the filler neck slowly go down - also for another ~10 seconds. Never thought much of it.

I feel like the previous owner said, in broken english, that it had a new fuel pump. He gave me every receipt he had which included every oil change down to wiper blades and his copy of a speeding ticket that he forgot to take out. You'd think he would have had the fuel pump receipt if he had actually said that. Anyway, maybe he gave up after doing the pump because that's not the underlying issue. I didn't prod at his reasons for getting rid of it because I quickly realized he spoke 1% English and I was feeling confident in my DIY inspection.

St Runner, will be doing just that. Happy that both you and CSP aren't suspecting things under the hood. Will report back

 

[hour]

This is the filter that I removed three weeks ago that was put on by the previous owner, no less than 3 years ago and ~15k miles. Doesn't look brand new, but it certainly doesn't look like the tar black filter media I've seen come out of others.

I tested to see whether a vacuum was forming in my tank causing the fuel pump to struggle. I drove without the gas cap on for 30 miles and it felt the same- awful. At the end of that 30 mile drive I pushed the fuel flapper down and there was no whoosh of air at all, so I don't that's causing my problem. Oddly enough, I did not throw a CEL doing this.

New fuel pump should be here at the beginning of next week. If that doesn't fix it, I'll see if I can bribe a Toyota tech from a local offroad group to check it. If he doesn't know, I'll try one round of diagnostics at the dealer. If that doesn't pan out, I'll sell the ***** for scrap.

 

[csp]

Oddly enough, I did not throw a CEL doing this.

You know that not everything will throw a CEL, right? Even with some sensors it takes a certain number of occurrences of the problem over time for the light on the dash to actually be illuminated as well.

IIRC, there's no fuel ventilation sensors in the T4R of this vintage.

IMO, that's a good call to replace the pump, based on the clean filter and other symptoms.

 

[hour]

You know that not everything will throw a CEL, right? Even with some sensors it takes a certain number of occurrences of the problem over time for the light on the dash to actually be illuminated as well.

IIRC, there's no fuel ventilation sensors in the T4R of this vintage.

IMO, that's a good call to replace the pump, based on the clean filter and other symptoms.

Well I kind of figured the first part to be true since I've never thrown a CEL after years of running like crap.. but assumed running with the cap off would surely do it based on what I've heard forever across all makes.

Anyway, will report back when I get the fuel pump in. Hoping for a drama-free install.

 

[shootmymime]

another important point is that on the connections between the pump and the hard lines there is a rubber hose. with ethanol fuel eats away at these rubber hoses and blows holes in them thus causing pressurized fuel after the pump to spray back into the tank and now making its way to the hard line and towards the fuel filter.

I saw this exact same thing happen to an work truck at work. one tank of ethanol fuel blew the hose apart and it lost all fuel pressure.

 

[hour]

another important point is that on the connections between the pump and the hard lines there is a rubber hose. with ethanol fuel eats away at these rubber hoses and blows holes in them thus causing pressurized fuel after the pump to spray back into the tank and now making its way to the hard line and towards the fuel filter.

I saw this exact same thing happen to an work truck at work. one tank of ethanol fuel blew the hose apart and it lost all fuel pressure.

Interesting, I'll be sure to inspect and replace anything I see down there that looks amiss. Don't want to go through dropping the tank only to have unanswered questions about the condition of tubes, wires, etc.

I've been thinking more about fuel pump voltage, so I'll likely do my best to rule that out before I bother dropping the tank. While the fuel filter changes bringing temporary relief still doesn't make any sense to me, I suppose a pump operating at less than optimum voltage could have problems overcoming normal amounts of back pressure.

Why the hell didn't they just add a valve under the hood for checking fuel pressure easily :ballchain:

 

[shootmymime]

Interesting, I'll be sure to inspect and replace anything I see down there that looks amiss. Don't want to go through dropping the tank only to have unanswered questions about the condition of tubes, wires, etc.



I've been thinking more about fuel pump voltage, so I'll likely do my best to rule that out before I bother dropping the tank. While the fuel filter changes bringing temporary relief still doesn't make any sense to me, I suppose a pump operating at less than optimum voltage could have problems overcoming normal amounts of back pressure.



Why the hell didn't they just add a valve under the hood for checking fuel pressure easily :ballchain:

Remove the rear seat carpet and open the access panel. There you can check voltage.

I don't think it's fuel filter clogging problem. It could be a clog in the line or a venting problem. From the fuel pressure regulator the drain back hose may be having problems.

Did you check your fuel pressure regulator? The vac hose attached to it fine.


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[hour]

Remove the rear seat carpet and open the access panel. There you can check voltage.

I don't think it's fuel filter clogging problem. It could be a clog in the line or a venting problem. From the fuel pressure regulator the drain back hose may be having problems.

Did you check your fuel pressure regulator? The vac hose attached to it fine.


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It's about to get dark so I didn't go any further. The hose from the FPR is new when i upgraded everything to silicone hoses - and it's connected, not split or damaged, and free of blockage. Not sure how else to give it a test.

I was delighted to see that the previous owner didn't hack a giant hole in the floor to access the tank, though it may have made my life easier... but I do see some evidence of wires not being in factory condition due to new vs old electrical tape.

The black female harness in pic was disconnected with no obvious male counterpart, what the heck would that ever connect to? Edit: oh... rear locker?

I was excited when I thought I saw some evidence of a melty harness, the white harness that goes down the access hatch. Turns out most of the brownish blobs are goop, but the harness is stained brown in some places, too. Idunno if it's dielectric gel that got cooked or what.

The opposite (vehicle) side, that comes up from the floor, doesn't have any evidence of getting too hot on the outside, and it looks ok inside..

And a pic of the brownish harness' connectors. Gross.

Gonna be a dirty job..

The harness in questionable condition just has four thin wires and after going through the access hatch run towards the rear of the vehicle. I wouldn't assume these are responsible for pump operation since they're so thin, and don't drop in to the tank from what I could see - since they run to the back of the car.

 

[JBurt]

Can you remove the pump without dropping the tank?

 

[shootmymime]

Can you remove the pump without dropping the tank?

By cutting a much larger hole in the floor yes. Other wise no.


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[csp]

OP you're grasping at straws again..

 

[hour]

Did the deed. Not too fun on a sloped driveway with 1/4 of a tank. The soft line for the tank vent was fused on to the hard lines as others have mentioned. I fought with it for too long before cutting it. Replaced it with 1/2" fuel line, which was a pain to get on as well and fits super snug.

I won't claim it's fixed for quite some time, since the first fuel filter replacement netted amazing results for a week, but I did turn it on and it purred beautifully so I know that it's running well for now. Finishing projector retrofit re-do and installing in a minute, then I'll hit the highway.

I'm kind of baffled though by the part # on this pump I pulled out. 195130-2772. All hits for that come back on foreign sites, and the only thing I can conclude is that it was often put in a 'Toyota HiAce' which did have a 3.4L v6 at some point.

Makes me wonder if I just removed the original fuel pump at 256,000 miles. The same thing happened when I replaced the MAF the other week, a Denso + Toyota stamped part, with a part # that only came back on foreign websites and nothing conclusive on whether it ever belonged with a 3.4L 4runner.

 

[hour]

Alright, well WTF.

So things immediately observed after 20 cranks to get the engine started, following fuel pump replacement and yet another filter change:

• Sounded better at idle, both cold and warm
• Practically no vibration through steering wheel or door panel at idle
• Pressing the gas after coasting would result in rpm+speed gain without having to mash it to force a downshift
• Car pulled hard from stop to redline at 50% throttle in the same time it previously would take to reach 3,000 rpms mashing it

It was a significant improvement over how it had been running, but it still didn't feel as strong as it had immediately after the first fuel filter change.

Anyway, took it over the mountain through Eisenhower tunnel, 11k ft / gain of 6k ft. I was actually able to keep pace at 65 on a hill that I can barely get up at 50 - with none of the foot to floor forced downshifts that would put me at 4500 unhealthy sounding rpms with no speed change. I even used cruise a lot on the way up because I didn't have to intervene.

So shortly after I get through the tunnel and coast miles and miles down the mountain, I put cruise back on and it does fine through the valley.. but as soon as I hit another hill, far smaller than any of the climbs I had been doing on the way up with cruise on, it wouldn't downshift, lost speed, and cruise control shut off.

The rest of the 130 miles of my drive were marginally better than it had been, but the pronounced vibration returned at idle and there were several hills where it just wouldn't do anything but lug when trying to climb a hill, and not downshift. I was stuck at 20mph up a hill through a neighborhood in Breckenridge with a Honda Fit and a Toyota Echo on my tail, foot to the floor - engine just lugged louder and louder without downshifting.

Highest coolant temp: 202*F
Highest transmission temp: 214*F

Trans temp dropped from 214*F as I exited the tunnel at the top of the mountain to 175*F when I started up the hill that made the problems very apparent again - coolant at 188*F.

Highlight: I cut my fuel vent tube 1.25" higher and my tank capacity was increased 3+ gal, projectors installed and somewhat aimed

 

[shootmymime]

And you've done sensors. Maf I remember you saying.
Do you have an air leak somewhere?
Is there a way you can check afr values?
Can you check air intake temps?
Engine temps?

I'm not sure if this is a lack of fuel problem of lack of air problem (sensors not reading correctly).

Is your transkickdown cable operating properly?


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[shootmymime]

Is your exhaust clear? Muffler? Cat? not plugged? does it get plugged as it heats up?

 

[hour]

And you've done sensors. Maf I remember you saying. Yep
Do you have an air leak somewhere? Not that spraying a can of starter fluid everywhere could reveal if so
Is there a way you can check afr values? I don't think that's an option on Torque app, which is what I'm limited to
Can you check air intake temps?Yeah, used to display that in Torque and it was always reasonable - truck was running crappy then too
Engine temps? Coolant temp at least, and I watch it like a hawk - always in a good range

I'm not sure if this is a lack of fuel problem of lack of air problem (sensors not reading correctly).

Is your transkickdown cable operating properly? All of the adjustable cables under the hood are tight, I can't imagine something like that would be a come and (occasionally) go problem


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Also worth mention, significant mention... 150 miles in to today's drive I did a 30 second hill climb on the highway then coasted for about a minute before I smelled gasoline. I was looking around for the culprit vehicle but there were two ~2 year old Subarus in front of me, and no one had passed in the opposite lane. The reality, is it was raw fuel - not a rich exhaust... I mean, I got covered in gas yesterday and had a tank in my face for a few hours - it was my car, and it was straight gas.

I couldn't pull over for a while and I know fuel evaporates fast, but I did check under the car to see if I didn't tighten anything properly. All was dry. I used a new tank gasket yesterday, the access hatch is reinstalled, and none of the soft lines were damaged when I inspected them. Plus- gas spraying under the back of the truck when I'm going 60 mph probably wouldn't flood the cab like it did. I had the fan on, pulling in fresh air.

So this could be another piece of the puzzle as I've never smelled raw gas inside my car and it doesn't appear to be from anything I did yesterday with the fuel pump. Injectors, FPR, charcoal canister?

 

[hour]

Is your exhaust clear? Muffler? Cat? not plugged? does it get plugged as it heats up?

Muffler has been on for a year and was new, cat is unknown age but I pass emissions and I also can't think it could have run ok for hundreds of hard working miles and then clog again

 

[shootmymime]

Also worth mention, significant mention... 150 miles in to today's drive I did a 30 second hill climb on the highway then coasted for about a minute before I smelled gasoline. I was looking around for the culprit vehicle but there were two ~2 year old Subarus in front of me, and no one had passed in the opposite lane. The reality, is it was raw fuel - not a rich exhaust... I mean, I got covered in gas yesterday and had a tank in my face for a few hours - it was my car, and it was straight gas.



I couldn't pull over for a while and I know fuel evaporates fast, but I did check under the car to see if I didn't tighten anything properly. All was dry. I used a new tank gasket yesterday, the access hatch is reinstalled, and none of the soft lines were damaged when I inspected them. Plus- gas spraying under the back of the truck when I'm going 60 mph probably wouldn't flood the cab like it did. I had the fan on, pulling in fresh air.



So this could be another piece of the puzzle as I've never smelled raw gas inside my car and it doesn't appear to be from anything I did yesterday with the fuel pump. Injectors, FPR, charcoal canister?

Yeah. So I have also had a fuel smell in my cab onetime. My 7th injector fitting had come loose and was dripping fuel on the top of the motor. I pulled over and tightened it no problems. So I know what you mean.

I wish there was a way you could check fuel pressure while driving. Also does removing the gas tank cap help. As you drive. The venting might not be working properly.

Now what I'm thinking is after you put some miles on the truck. The vacuum from fuel leaving the tank could be a problem for the pump. (Shouldn't but could). That's the hissing noise as you open the cap of the fuel tank.

Now another problem I've seen (in hot Moab). A 2nd gen was having the tank pressurized from the high heat and causing the EFI fuse to blow and truck to stall.

What are your thoughts as the gas tank going under vacuum or pressure? Is a new gas cap a possibility?

What do your spark plugs look like?